fix/paragraphs (#5431)

Currently implements both a format hook to remove white-space paragraphs, and a check to make their existence a critical failure.

In the end may implement only one or none of these, subject to major design changes.

Solves #5409

Co-authored-by: Darragh Elliott <me@delliott.net>
Reviewed-on: #5431
Co-authored-by: delliott <delliott@fsfe.org>
Co-committed-by: delliott <delliott@fsfe.org>

fsfe.org/freesoftware/secure-boot.de.xhtml

@@ -1,5 +1,4 @@
-<?xml version="1.0" encoding="UTF-8" ?>
-
+<?xml version="1.0" encoding="utf-8"?>
 <html>
   <version>1</version>
 
@@ -218,13 +217,12 @@ und letztendlich die exklusive Kontrolle über die eigenen Daten sicher zu stell
 
   </body>
 
-  <sidebar promo="our-work" />
+  <sidebar promo="our-work"/>
 
-  <author id="kirschner" />
+  <author id="kirschner"/>
   <date>
-    <original content="2012-06-01" />
+    <original content="2012-06-01"/>
   </date>
   <translator>Flo</translator>
   <translator>Aljosha Papsch</translator>
 </html>
-